Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch panel, which can be a clear panel with a touch-sensitive surface. The touch panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens can allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen can recognize the touch and position of the touch on the display screen, and the computing system can interpret the touch and thereafter perform an action based on the touch event.
Recent touch panels can detect multiple touches and near touches (within the near-field detection capabilities of their touch sensors) occurring at about the same time, and identify and track their locations. Examples of multi-touch panels are described in Applicant's co-pending U.S. application Ser. No. 10/842,862 entitled “Multipoint Touchscreen,” filed on May 6, 2004 and published as U.S. Published Application No. 2006/0097991 on May 11, 2006, and U.S. application Ser. No. 11/649,998 entitled “Proximity and Multi-Touch Sensor Detection and Demodulation,” filed on Jan. 3, 2007, the contents of both which are incorporated by reference herein.
Capacitive touch sensor panels can include an array of sensors or pixels formed by drive lines and sense lines in proximity with each other. The drive lines can be driven by stimulation signals, and the change in capacitance at one or more pixels can be detected by receive channels coupled to the sense lines. Each receive channel can include a charge amplifier, anti-aliasing filter, analog-to-digital converter (ADC) and subsequent digital demodulation. Alternately, demodulation can be performed prior to ADC conversion. ADCs can consume large amounts of power dependent on topology, speed and resolution. Accordingly, it can be desirable to reduce the amount of power consumed by the ADCs by implementing a suitable ADC topology and further optimizing of the selected ADC topology.